1. Field of the Invention
The present invention relates generally to an apparatus for chemical testing. More particularly, it relates to a chamber suitable for exposing cell cultures to volatile chemicals or hazardous materials.
2. Description of the Related Art
The use of cell culture systems has gained increased importance in the area of toxicity research. The recent push to reduce or replace test animals with in vitro testing has been a significant driver of this change. In many applications, chemicals that exhibit good potential for industrial or military use may be quite volatile. This poses a problem both in the potential for personnel exposure to possibly hazardous chemicals and in safety testing of such exposure. A major challenge for the in vitro testing of volatile chemicals is that in contrast to an animal system, which uptakes vapor through breathing, cell cultures are xe2x80x9copenxe2x80x9d and rely on diffusion of chemicals into culture media before the chemicals enter the cells. The volume of the atmosphere in the surrounding chamber generally is much greater than the volume of the culture media or of cells in culturing vessels. Another major challenge arises from the inherent properties of the chemicals. Volatile chemicals are readily lost by diffusion out of cells and culture media into the atmosphere. This poses a problem in assessing the toxicity of such chemicals because as time progresses during an experiment and chemicals are lost, the actual dose to which cells are exposed changes, resulting in a lower and uncontrolled dose over time.
Previous attempts to address these problems have employed plastic bags or plastic containers to create a closed system in which culture vessels can be placed. This approach suffers from a number of disadvantages. For example, the use of plastics in cell culture systems can be disadvantageous, since volatile organic materials are known to absorb (partition) into plastics, thus leading to dosimetry problems and chamber contamination. Furthermore, plastics commonly used for containers react poorly to repeated autoclaving. Also, such closed systems do not allow for the constant regulation of the vital atmosphere (such as the oxygen and carbon dioxide content) with or without chemical additives, or for efficient sampling of the atmosphere within the systems.
Accordingly, the present invention provides an exposure chamber suitable for use in exposing cell cultures to volatile and potentially hazardous chemicals.
The present invention also provides an exposure chamber that can be made of substantially inert and impermeable materials so at not to react with or absorb chemicals contained therein.
The present invention additionally provides an exposure chamber with sufficient thermal stability to protect the interior of the chamber from temperature changes when the chamber is moved from one room or environment to another, or when substances are added to or removed from the chambers.
The present invention yet further provides an exposure chamber that can be stacked with one or more other chambers, one atop another.
The present invention also provides an exposure chamber which enables objects to be placed into or removed from the exposure chamber while the exposure chamber is disposed in a stack with one or more other exposure chambers.
The present invention additionally provides an exposure chamber which enables chemicals to be introduced into the exposure chamber and enables samples to be removed from the exposure chamber while the chamber is closed.
According to one form of the present invention, an exposure chamber for cell cultures includes a chamber body having an opening through which cell cultures can be introduced and a lid detachably mounted on the opening. When the lid is removed from the opening, cell cultures in culturing vessels can be introduced into or removed from the chamber body. The chamber preferably includes one or more fluid ports through which a fluid, such as an atmosphere to which cell cultures are to be exposed, can be introduced into the chamber when the chamber body is closed by the lid. In preferred embodiments, the chamber body and the lid are made of glass.
In preferred embodiments, the lid is capable of being mounted on and removed from the chamber body with the chamber disposed above or below another chamber in a stack. Preferably, adjoining chambers in a stack can engage with each other to prevent relative horizontal movement of the chambers.
According to another form of the present invention, a method of culturing cells includes placing a cell culture into a chamber, closing the chamber, introducing an atmosphere into the closed chamber via a fluid port of the chamber, and placing the chamber into an incubator. In a preferred embodiment, an atmosphere is introduced into the closed chamber from a bag or other compressible container in which the atmosphere has previously been prepared and which is compressed to force the atmosphere into the chamber. A previously existing atmosphere within the chamber may be displaced by the introduced atmosphere in another compressible container. The interior of the chamber may be sampled through a port of the chamber.
A standard incubator can generally expose the cell cultures therein to only a single atmosphere at one time. In contrast, by using a plurality of exposure chambers according to the present invention disposed in an incubator, the cell cultures in different exposure chambers can be exposed to different atmospheres simultaneously, enabling the incubator to be utilized much more efficiently. Since the atmospheres within the exposure chambers are isolated from the atmosphere surrounding them in the incubator, the atmosphere of the incubator itself does not need to be controlled, permitting a decrease in the operating costs of the incubator.
A standard incubator generally has an internal volume much larger than that required by cell cultures disposed therein, so when the incubator is filled with a special atmosphere, the amount of chemicals or gas required to create the atmosphere may far exceed the volume actually required for culturing. In an exposure chamber according to the present invention, the head space of the exposure chamber (the space between the cell cultures and the upper inner surface of the exposure chamber) can be reduced to the minimum necessary to provide the cell cultures in the chamber the volume of atmosphere they need to survive. Therefore, the volume of gases and chemicals needed to create a desired atmosphere can be greatly decreased.
An exposure chamber according to the present invention also provides a convenient way to transport cell cultures from place to place while isolating the cell cultures from the environment. The exposure chamber can insulate cell cultures inside it against changes in temperature, humidity, or atmospheric content as the cell cultures are transported, and it can protect lab workers against toxic chemicals which may be present in the exposure chamber. The ports on the exposure chamber enable gases and chemicals to be introduced into or removed from the exposure chamber in a highly controlled manner, thereby reducing the risk to lab workers by avoiding contact with the gases or chemicals.